When a semiconductor device is manufactured, various kinds of heat processing apparatuses are employed for subjecting a semiconductor wafer, which is an object to be processed, to processes such as an oxidation process, a diffusion process, and a CVD (Chemical Vapor Deposition) process. A general heat processing apparatus includes a heat processing furnace which is composed of: a processing vessel (also referred to as “reaction tube”) in which a semiconductor wafer can be accommodated and heat-processed; a heating resister (also referred to as “heating wire” or “element”) disposed around the processing vessel; and a heat insulation member disposed around the heating resistor. The heating resistor is arranged on an inner wall surface of the heat insulation member via a support member (see, Patent Document 1).
In a heat processing apparatus capable of performing a batch process, for example, there is used, as the heating resistor, a helical heating resistor arranged along an inner wall surface of a cylindrical heat insulation member. The heating element can heat an inside of the furnace to a high temperature such as about 800° C. to 1000° C. As the heat insulation member, there is used a member that is formed by burning a heat insulation material, such as ceramic fibers, into a cylindrical shape. The heat insulation member can reduce a heat quantity which is lost as radiant heat and conductive heat, so as to enhance efficiency in heating. As the support member, there is used a ceramic member having a comb-like shape, for example. The ceramic support member can support the heating resistor at predetermined pitches, while allowing a thermal expansion and a thermal shrinkage of the heating resistor. In such a heat processing furnace, the heating resistor is formed to have a helical shape, and is supported such that a clearance is defined between the heating resistor and the heat insulation member for allowing the thermal expansion and the thermal shrinkage. Thus, different from a heating resistor which is embedded in a heat insulation member, heat confinement in the heating resistor itself can be prevented, and an object to be heated (wafer) can be directly heated. Accordingly, it is possible to improve durability of the heating resistor (to extend a lifetime), to save energy, and to rapidly increase and decrease a temperature.    [Patent Document 1] JP10-233277A
In a conventional heat processing furnace, as shown in FIG. 21, a support piece of a support member 13 for supporting a heating resistor 5 has a rectangular shape in cross-section. Namely, the heating resistor 5 is supported by a corner portion 50 of the support piece 18. Thus, when the heating resistor 5 is thermally expanded or thermally shrunk, a large frictional resistance is generated between the support piece 18 of the support member 13 and the heating resistor 5, so that movement of the heating resistor is inhibited. In this case, the heating resistor undergoes a permanent deformation caused by a residual stress, which invites deterioration in durability (reduction in lifetime). In particular, when the heating resistor is heated to be thermally expanded and then cooled to be thermally shrunk, there is a tendency that a permanent elongation (permanent deformation) of the heating resistor is promoted by the residual stress caused by the frictional resistance between the support member and the heating resistor, resulting in deterioration in durability of the heating resistor.